Spring-steel.



- physical properties. Among the other obunrrno srarns PATENT oniuon.

CHILD HAROLD WILLS, 0F DETROIT, MICHIGAN. I

SPRING-STEEL.

Specification of Letters Patent. Patented Dec. 17, 1918.

No Drawing. Original application filed June 19, 191?, Serial No. 173,719: Divided and this application filed August 7, 1917. Serial No. 184,942.

To all whom it may concern:

Be it known that I, CHILD H'ARoLoWmLs, a citizen of the United States, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Spring-Steels, of which the following is a specification.

This invention relates to spring steels for use in the manufacture of springs for automobiles and the like, and it is a division of my copending application, Serial Number 173,719 filed June 19th, 1917. I

It is one of the primary objects of my invention to provide a spring steel which will have a, maximum resistance to alternating stresses and, at the same time, have superior I ]ects of my invention is the provision of a steel having the characteristics described which is economical to manufacture, easily worked, and which has an increased range of heat treatment temperatures, theadvantages of which will hereinafterbe more fully set out.

In the usual classes of spring steel at present in use, diiiicultieshave been encountered in a number of important respects. In the first place it is impossible/in such steels to obtain maximum resistance to alternating stresses, and at the same time obtain maximum physical properties, for the reason that the resistance to alternating stresses increases as the annealing temperature approaches the critical point, while the physical properties decrease. If the carbon content be increased to increase the physical properties, the liability to cracking when the steel is quenched and the development of other defects and undesirable characteristics are increased. Furthermore, the range of temperaturewithin which suchsteels must be treated" is very narrow which of course, frequently results in losses in manufacture and failure in service, because of'the difiiculty of maintaining furnace temperatures uniform. my present invention I overcome the foregoing difficulties, obtain a greatly increased range of temperature for heat treatment and the steels at the same time have superior depth hardening charac teristics.

I accomplish the foregoing by adding to spring steel, molybdenum in small percentages, preferably from a substantial fraction of 1% up to about 1%. I find that such molybdenum spring steel can be manufactured more economically than ordinary spring steels for the reason that the molybdenum increases the yield by decreasing the amount of croppage .or discard and the amount of grinding necessary. This results from the fact that the tendency to scam or to, pipe is greatly reduced, and in addition, the molybdenum does not segregate and apparently overcomes the tendency of theother alloying elements to segregate, which of course, causes the steel to run more uniformly throughout. From the steel makers" standpoint, therefore, such molybdenum is not only economical to make but it is superior in quality. i

In so far as manufacture is concerned, the steel is superior for the reason that the molybdenum greatly increases the temper ature range for heat treatment and thus obviates the necessity for complicated furnace regulating equipment, and greatly reduces the losses ordinarily incurred when the allowable limits of temperature are exceeded. In ordinary steels when the narrow range of temperatureis exceeded, the prop erties of the steel are greatly impaired, but

in steel made in accordance with my inven-,.-

tion, the ordinary range of heat treatment can be greatly exceeded Without detrimental structural and chemical change. At the same time the steel isreadily workable and has superior depth hardening characteristics, as above noted. As a result of the increase in temperature-range, the'steel runs uniformly.

With regard to the article produced, 11. 6., the performance of the springs, the use of molybdenum not only increases the resistance to alternating stresses but also greatly increases the physical properties, so that the springs will be strong enough to support the load and Withstand shock without, perma-' nent setting To illustrate, in spring steels made in accordance with my'invention, a.

, creased physical properties, the steel is.

1 denum content phasized by the fact that the resistance to alternating stresses without crystallization is greatly increased, and by the fact that the molybdenum increases the depth of hardening. NothWi-thstanding these greately inreadily workable. 1

y In carrying out my invention I prefer the following analyses as giving the most sat isfactory results, namely, carbon from 38% to .55 b;-manganese from .4070 to 1.25

chromium from a fraction of a per cent, to 2%; silicon from 10% to 40%; and molybdenum in substantial fractional percentages up to 1%. l find that if the molybbe materially carried above 1% the steel d velops undesirable characteristics. It Will also be understood that the manganese and chromium may be replaced by equivalent elements or omitted, but these are preferred because the molybdenum inlessees tensifies the efiect of the other alloys, particularly the chromium. I also prefer to draw the steel at temperatures ranging approximately from 1020* F. to 1100 F., or

stated in other Words,I prefer to draw ma 1. Heavy duty spring steel contamingimolybdenum in quantities not materially exceeding 1% and drawn materially above 320 C.

2. Spring steel carbon from 58% to 55%; manganese from -4:0% to"l.25%; chromium from a fraction to 2% silicon from 10% to 411%; and molybdenum from a fraction to 1%, substantially as set forth. In testimony whereof I have hereunto signed my name.

- f CHILD HAROLD WILLS. 

